This invention relates to a facsimile signal transmission system for enhancing facsimile signal transmission efficiency in facsimile communication in an international public switched network, an intra-enterprise communication network, etc.
In a facsimile signal transmission system, a DCS signal, an EPT signal, a training signal, a TCF signal, an image signal, and a control signal of facsimile signals are output from a transmission facsimile terminal to a reception facsimile terminal in sequence, whereby the facsimile signals are transmitted.
The DCS signal is a digital command signal of a facsimile signal output from the transmission facsimile terminal. It is output after a digital identification signal (DIS) of a facsimile signal output from the reception facsimile terminal is received. The capabilities of the reception facsimile terminal (modulation system, modulation speed, receivable original picture sizes, resolution, etc.,) are recognized according to the received DIS and are compared with the capabilities of the transmission facsimile terminal for judging communicatable capabilities. The judgement result is returned to the reception facsimile terminal as the DCS signal.
The EPT signal is an echo protect tone signal for instructing an echo canceller existing in a transmission path for facsimile communication to stop the operation. After the signal is received, the echo canceller existing in the transmission path stops the echo cancel operation.
The training signal is a signal for training a reception section (demodulation section) in the reception facsimile terminal so as to correctly receive the image signal and the TCF signal.
According to the signal, a synchronizing circuit, an adaptive equalizer, and the like in the demodulation section are trained for the functions required for correctly receiving the image signal.
The TCF signal is a training check signal for checking to see if the circuits, etc., are trained correctly by the training signal so that later the image signal can be received correctly. It is a signal with xe2x80x9c0xe2x80x9d data modulated for 1.5 seconds and is used to determine whether or not xe2x80x9c0xe2x80x9d can be received correctly for a given time at the reception facsimile terminal.
The image signal is a signal for indicating original picture data.
The control signal includes the DCS signal, an EOP signal, etc. The EOP signal is a signal for indicating the end of original data transmission.
After the signals are transmitted and received, a facsimile communication termination procedure is executed.
A flag signal is transmitted before the facsimile control signals (DCS signal, EOP signal, etc.,) other than the TCF signal or the image signal. It is a synchronizing signal for receiving the control signals. The flag signal is a signal with xe2x80x9c7Exe2x80x9d data modulated for one second.
An example of facsimile signal transmission equipment in a related art is a digital circuit multiplication equipment (DCME) applied to an international public switched network. Facsimile signal transmission system for DCME is described in ITU-T Recommendation G.766 and a part of the facsimile signal transmission system in the digital circuit multiplication equipment is shown in FIGS. 17 to 20.
FIG. 17 is a flowchart in the facsimile signal transmission system for transmission DCME to output a DCS signal, an EPT signal, a training signal, And a TCF signal output from a transmission facsimile terminal to reception DCME.
FIG. 18 is a flowchart in the facsimile signal transmission system for the reception DCME to output the DCS signal, the EPT signal, the training signal, and the TCF signal of the facsimile signals output from the transmission DCME to a reception facsimile terminal.
FIG. 19 is a flowchart in the facsimile signal transmission system for the transmission DCME to output an image signal and a control signal output from the transmission facsimile terminal to the reception DCME.
FIG. 20 is a flowchart in the facsimile signal transmission system for the reception DCME to output the image signal and the control signal of the facsimile signals output from the transmission DCME to the reception facsimile terminal.
Next, the operation will be discussed.
First, a transmission system of the DCS signal, the EPT signal, the training signal, and the TCF signal in the DCME will be discussed. For convenience of the description, FIG. 21 shows a transmission sequence of these signals between the transmission facsimile terminal and the reception facsimile terminal.
The transmission facsimile terminal sends the DCS signal, one of facsimile control signals, indicating the capabilities of the transmission facsimile terminal such as the modulation system, the modulation speed, and receivable image resolution in accordance with transmission sequence defined in ITU-T Recommendation T.30, then sends the EPT signal for 185 ms to 200 ms in a silent time of 75 msxc2x120 ms and subsequently sends the training signal and the TCF signal in a silent time of 20 ms to 25 ms.
As shown in FIGS. 17 and 21, the transmission DCME detects the end of the DCS signal, then sends an IDLE message signal indicating the end of the DCS signal to the reception DCME. Subsequently, the transmission DCME sends an EPT massage signal after detecting the EPT signal, an END_EPT message signal after detecting the end of the EPT signal, a TRAINING message signal after detecting the training signal, and a FAX_DATA message signal after detecting the end of the training signal to the reception DCME (ST80 to ST87). After this, the transmission DCME sends the TCF signal to the reception DCME.
On the other hand, as shown in FIGS. 18 and 21, after receiving the EPT message signal from the transmission DCME (ST91), the reception DCME sends the EPT signal to the reception facsimile terminal (ST92) until reception of the END_EPT message signal (ST93). Next, after receiving the TRAINING message signal from the transmission DCME (ST94), the reception DCME sends the training signal to the reception facsimile terminal (ST95) until reception of the FAX_DATA message signal (ST96).
Next, a transmission system of the image signal and the control signal in the DCME will be discussed. For convenience of the description, FIG. 22 shows a transmission sequence of these signals between the transmission facsimile terminal and the reception facsimile terminal. It shows a sequence for transmitting an original of only one page between the facsimile terminals as an example.
The transmission facsimile terminal sends facsimile image signal corresponding to one page of facsimile image, then sends a flag signal in a silent time of 75 msxc2x120 ms and subsequently an end-of-procedures signal (EOP signal), one of the facsimile control signals.
As shown in FIGS. 19 and 22, the transmission DCME detects the end of the image signal (ST100), then sends an IDLE message signal indicating the end of the image signal to the reception DCME (ST101). Subsequently, the transmission DCME detects the flag signal (ST102), then sends a SIGNALLING message signal (ST103), then sends flag and EOP signals.
On the other hand, as shown in FIGS. 20 and 22, the reception DCME receives the SIGNALLING message signal from the transmission DCME (ST111), then sends the flag signal and the EOP signal received from the transmission DCME to the reception facsimile terminal.
Since the facsimile signals are thus transmitted between transmission and reception facsimile terminals in the facsimile signal transmission system in the related art, it is feared that the time interval of facsimile signal sent from the transmission facsimile terminal defined in Recommendation T.30 may not be held. Specifically, in FIG. 21, it is feared that the EPT message signal may arrive at the reception DCME after the expiration of 95 ms or more because of detection delay of the EPT signal in the transmission DCME and sending delay of the EPT message signal to the reception DCME. In this case, the time interval between the DCS signal sending end and the EPT signal sending start in the reception DCME becomes 95 ms or more. It is also feared that the EPT sending time to the reception facsimile terminal may become shorter than the stipulated time.
Further, it is feared that the TRAINING message signal may arrive at the reception DCME after the expiration of 25 ms or more because of detection delay of the training signal in the transmission DCME and sending delay of the TRAINING message signal to the reception DCME. In this case, the time interval between the EPT signal sending end and the training signal sending start in the reception DCME becomes 25 ms or more.
Likewise, in FIG. 22, it is feared that the SIGNALLING message signal may arrive at the reception DCME after the expiration of 95 ms or more because of detection delay of the flag signal in the transmission DCME and sending delay of the SIGNALLING message signal to the reception DCME. In this case, the time interval between the image signal sending end and the EOP signal sending start in the reception DCME becomes 95 ms or more.
If a signal not satisfying the time interval defined in Recommendation T.30 as described above is received, the reception facsimile terminal judges that the signal is a communication error, and the communication erroneously terminates at the worst.
It is therefore an object of the invention to provide a facsimile signal transmission system which satisfies the stipulation of the signal sending time and the stipulation of the signal time interval for enabling successful facsimile communication even if a detection delay or a sending delay as described above occurs.
According to the invention, there is provided a facsimile signal transmission system for outputting a digital command signal (DCS signal), an echo protect tone signal (EPT signal), a training signal, a training check signal (TCF signal), an image signal, and a control signal of facsimile signals in sequence from a transmission facsimile terminal to a reception facsimile terminal, wherein if an IDLE message signal output from a transmission party at the end of the DCS signal is received in a reception party, a first timer operated for a first predetermined time is started, wherein when the first predetermined time has elapsed, sending of the EPT signal to the reception facsimile terminal is started, wherein a second timer operated for a second predetermined time is started at the same time as sending of the EPT signal is started, wherein when the second predetermined time has elapsed, sending of the EPT signal is terminated, wherein a third timer operated for a third predetermined time is started at the same time as sending of the EPT signal is terminated, and wherein when the third predetermined time has elapsed, sending of the training signal to the reception facsimile terminal is started.
If the TCF signal is received from a transmission party while the training signal is being sent, TCF signal data is stored until sending of the training signal terminates.
To output the TCF signal to the reception facsimile terminal, if a FAX_DATA message signal output from the transmission party at the end of the training signal is received in the reception party, the TCF signal is output to the reception facsimile terminal and on the other hand, while no FAX_DATA message signal is received, a dummy signal generated in the reception party is output to the reception facsimile terminal.
According to the invention, there is provided a facsimile signal transmission system for outputting a DCS signal, an EPT signal, a training signal, a TCF signal, an image signal, and a control signal of facsimile signals in sequence from a transmission facsimile terminal to a reception facsimile terminal, wherein if the end of the DCS signal is detected in a transmission party, a first timer operated for a first predetermined time is started, wherein when the first predetermined time has elapsed, an EPT message signal is sent to a reception party and a second timer operated for a second predetermined time is started, wherein when the second predetermined time has elapsed, an END_EPT message signal is sent to the reception party and a third timer operated for a third predetermined time is started, and wherein when the third predetermined time has elapsed, a TRAINING message signal is sent to the reception party and after the expiration of a predetermined training time, a FAX_DATA message signal is sent.
If the TCF signal is received from the transmission facsimile terminal in a training time end wait state, the TCF signal is stored until the end of the predetermined training time.
The TCF signal output from the transmission facsimile terminal is output to the reception party and on the other hand, while no TCF signal is received, a dummy signal generated in the transmission party is output to the reception party.
Fill data is used as the dummy signal.
According to the invention, there is provided a facsimile signal transmission system for outputting a DCS signal, an EPT signal, a training signal, a TCF signal, an image signal, and a control signal of facsimile signals in sequence from a transmission facsimile terminal to a reception facsimile terminal, wherein if an IDLE message signal output from a transmission party at the end of the image signal is received in a reception party, a timer operated for a predetermined time is started and wherein if a SIGNALLING message signal is received from a transmission party after the expiration of the predetermined time, sending of a flag signal received from the transmission party to the reception facsimile terminal is started and on the other hand, if no SIGNALLING message signal is received from the transmission party, a dummy signal generated in the reception party is sent to the reception facsimile terminal.
According to the invention, there is provided a facsimile signal transmission system for outputting a DCS signal, an EPT signal, a training signal, a TCF signal, an image signal, and a control signal of facsimile signals in sequence from a transmission facsimile terminal to a reception facsimile terminal, wherein if the end of the image signal is detected in a transmission party, a timer operated for a predetermined time is started, wherein a SIGNALLING message signal is output to a reception party after the expiration of the predetermined time, and wherein sending of a flag signal to the reception party is started and on the other hand, if flag signal transmission to the reception party is not started, a dummy signal generated in the transmission party is sent to the reception party.
Flag data is used as the dummy signal.
According to the invention, there is provided a facsimile signal transmission system for outputting a DCS signal, an EPT signal, a training signal, a TCF signal, an image signal, and a control signal of facsimile signals in sequence from a transmission facsimile terminal to a reception facsimile terminal, wherein a facsimile control signal output from a transmission party after the end of the image signal is not output from a reception party to the reception facsimile terminal and a second facsimile control signal output from the transmission party is output to the reception facsimile terminal.
According to the invention, there is provided a facsimile signal transmission system for outputting a DCS signal, an EPT signal, a training signal, a TCF signal, an image signal, and a control signal of facsimile signals in sequence from a transmission facsimile terminal to a reception facsimile terminal, wherein after the end of the image signal, a facsimile control signal is not output from a transmission part to a reception party and a second facsimile control signal output from the transmission facsimile terminal is output to the reception party.